This invention relates to an ac plasma display requiring a reduced amount of driver circuitry and, more particularly, to such a display having selective horizontal and vertical shifting capability.
A plasma panel is a display device comprised of a body of ionizable gas sealed within a nonconductive, usually transparent envelope. Alphanumerics, pictures, and other graphical data are displayed by controllaby initiating glow discharges (also referred to as "gas discharges") at selected locations (sites) within the display gas. This is accomplished by setting up electric fields within the gas via appropriately arranged electrodes, or conductors.
The invention principally relates to so-called ac plasma panels which have the conductors embedded within dielectric layers disposed on two opposing nonconductive surfaces, such as glass plates. Typically, the conductors are arranged in rows on one plate and columns orthogonal thereto on the other plate. The overlappings, or crosspoints, of the row and column conductors define a matrix of discharge cells, or sites. Glow discharges (the ON-site condition) are initiated at selected crosspoints under the control of, for example, a digital computer.
A priorly filed copending patent application of P. D. T. Ngo, known as Ser. No. 109,859, filed Jan. 7, 1980, now U.S. Pat. No. 4,328,489, is directed, inter alia, to a technique for providing self-shifting of the ON display sites of an ac plasma panel. In that application lateral shifting is accomplished using a four-phase technique operating in a manner to cause display site discharge transportation from an ON display site to a next adjacent site position. Using the four-phase technique, it is possible to connect together each fourth column conductor, resulting in the use of only four column drivers as opposed to one driver for each column conductor. This technique requires a separate driver for each of the row conductors. In a typical visual display pattern, each pattern includes a 13-row by 9-column matrix for each of 39 character lines which totals 507 row conductors each requiring driver circuitry.
Another approach involves utilizing a plasma panel with a lower staging area for receiving input display data and an upper viewing, or exhibiting, area with both areas sharing common vertical conductors is disclosed in another copending patent application of P. D. T. Ngo, Ser. No. 307,169, filed Sept. 30, 1981. The upper viewing area shares four row drivers in a multiplexed shifting arrangement. However, this requires additional circuitry to apply signals to produce an electric field advanced in time in that section of the panel to prevent lateral shifting.
It would be highly desirable to have a plasma panel which possesses both a staging area and an exhibiting area yet is capable of being driven by a minimum number of drivers without the necessity of additional circuitry to prevent shifting of the ON sites in the viewing area.